1. Field of the Invention
This invention relates to water insoluble crosslinked homopolymers and copolymers formed on an inert substrate by the addition polymerization of monomers containing ethylenic unsaturation.
2. Description of the Prior Art
Polymers and copolymers of N-vinyl lactams and particularly N-vinyl pyrrolidone have been heretofore produced in insoluble form. As used herein the term "insoluble" is intended to define products which are insoluble in water, strong mineral acids, caustic solutions and common organic solvents. Illustrative insoluble polymers of N-vinyl lactams are those represented by the polyvinyl pyrrolidones of U.S. Pat. Nos. 3,216,579; 2,927,913 and 3,511,823, as distinguished from the polyvinyl pyrrolidones such as represented by U.S. Pat. Nos. 2,265,450 and 2,335,454.
It is known that beverages such as beer can be purified when contacted with inorganic clay carriers coated with a vinyl resin such as polyvinyl acetate or a poly N-vinyl pyrrolidone, as disclosed for example in U.S. Pat. No. 3,424,588, or with polyvinyl pyrrolidone which has been crosslinked or complexed with polyacids such as polyacrylic and tannic acids and their derivatives.
It has been found that polymeric selective adsorbents heretofore employed were not as effective as might be desired. A primary difficulty with these adsorbents is that they do not efficiently utilize the potentially available active sites. When employed as fine powders of the polymeric material, a large proportion of the potentially active sites is buried within the polymeric particle and is thus not available for adsorption. And, even when these polymers are coated on inert carriers by conventional coating techniques, the coating thickness is so great that a large proportion of the potentially active sites remain unavailable for adsorption. The present invention, however, embraces means for overcoming these difficulties, and provides improved polymeric selective adsorbents useful for purification of beverages, such as beer, by complexing undesirable dissolved materials from the liquid, and removing them by filtration; and a method for obtaining a uniform, shape-stable insoluble, as well as a crosslinked polymeric film on an inert carrier.